Wireless communications in the United States were initially conducted solely through analog systems and protocols. The most prevalent analog protocol remains the Advanced Mobile Telephone System (AMPS) protocol. To handle wireless communications and to allow interconnection with traditional wired land-lines, switching systems and base stations were required. The analog switching systems are large and are designed to cover large markets and handle large volumes of calls.
In the 1990's digital systems and protocols began to be used for wireless communications. Examples of digital protocols are the Global System for Mobile Communication (GSM) code division multiple access (CDMA), and time division multiple access (TDMA). When wireless networks began to switch to digital protocols, they could not simply upgrade their analog base stations to digital. New equipment for the digital facilities was required. However, the networks continued to use large switching systems designed to cover their large spread markets. Examples of large switching systems are AT&T's 5ESS® system and the AXE system made by Ericsson. The 5ESS® switch is described in detail in the AT&T Technical Journal, Vol. 64, No. 6, part 2, July/August 1985, pages 1305-1564.
Large switching systems are designed to cover large markets and to handle many thousands of customers. The larger systems have the advantage of being able to provide a wide range of call options, such as call forwarding, caller identification and call waiting. The switching systems are expensive, however and, therefore, may not be appropriate for small markets and wireless providers. Additionally, large switching systems can be inefficient because of the added additional cost for increased back hauls of calls.
Typical switching systems employ proprietary architectures that use hardware components for switching, external interfaces, operating system, and control.